1. Field of the Invention
This invention relates generally to electronic whiteboard for illustration display and for capturing contents of discussion writing or drawing on the surface of the board as digital data. More particularly, this invention is related to new and improved electronic whiteboards formed with electrophoretic cell array for receiving display inputs from both manual operations with electric or magnetic pen to write and draw on the surface of the board and from digital input signals to the electrophoretic cell array.
2. Description of the Prior Art
The usefulness of a conventional electronic whiteboard is still limited by a single input-mode operation that an electronic whiteboard can only receive input by manually writing or drawing directly on the surface of the whiteboard using an electric or magnetic pen. Since it allows only manual operations on the surface of the board, real time displays in a meeting for immediate viewing and discussion of more complicate or detail illustrations may become very inconvenient unless manual efforts are employed to draw the details of such illustrations before the meeting. Furthermore, limited by this manual input-mode of configuration and operation, a conventional electronic whiteboard is not able to receive signal input from an electronic file that contains graphic or textual contents as displayable elements. There is still a gap that prevents direct communications between the conventional whiteboards and the media-rich contents broadly available as electronic files ready for display on many different kinds of media display devices. Due to these limitations, the conventional whiteboard still remains basically as a write/draw then copy device employed to record the hand writing information. As a hand-writing input device, a conventional electronic whiteboard is further limited by the disadvantage that dust or debris from using color chalks or ink for writing on the board may cause health and environmental hazards.
For these reasons, instead of electronic whiteboard, image projections applying liquid crystal display (LCD) or MEM projector are often selected to display images for discussions in a meeting, particularly when illustrations of more complicated or detailed images are necessary. However, image projection display often requires projection equipment of higher cost. In order to have a better view of the projected images, a low lighting background is often required. The greatest disadvantage of using the projected images for discussion is the limitation that the projected images can only be changed from a computer. An option of making changes with handwriting or drawing on the projected images is not available. For the purpose of providing images for real-time discussion, this limitation significantly reduces the effectiveness of real time presentation and discussions. Furthermore, in order to project the image on a display surface, a person making presentation or coordinating a discussion must stay away from the projection light so that the projected images are not blocked. Also, when such person standing next to the display images facing the projection lights, a view of the audience or meeting participants for sensing their reactions to the displayed images and the discussions is further hindered. Therefore, there is still a need in the art of image display to provide improved methods and devices such that these difficulties and limitations can be overcome.
An electrophoretic display (EPD) is a non-emissive device based on the electrophoresis phenomenon influencing charged pigment particles suspended in a colored dielectric solvent. This general type of display was first proposed in 1969. An EPD typically comprises a pair of opposed, spaced-apart plate-like electrodes, with spacers predetermining a certain distance between the electrodes. At least one of the electrodes, typically on the viewing side, is transparent.
When a voltage difference is imposed between the two electrodes, the pigment particles migrate by attraction to the plate of polarity opposite that of the pigment particles. Thus, the color showing at the transparent plate, determined by selectively charging the plates, can be either the color of the solvent or the color of the pigment particles. Reversal of plate polarity will cause the particles to migrate back to the opposite plate, thereby reversing the color. Intermediate color density (or shades of gray) due to intermediate pigment density at the transparent plate may be obtained by controlling the plate charge through a range of voltages or pulsing time. EPDs of different pixel or cell structures have been reported previously, for example, the partition-type EPD (M. A. Hopper and V. Novotny, IEEE Trans. Electr. Dev., 26(8):1148-1152 (1979)) and the microencapsulated EPD (U.S. Pat. Nos. 5,961,804 and 5,930,026).
An improved EPD technology was recently disclosed in co-pending applications, U.S. Ser. No. 09/518,488, filed on Mar. 3, 2000 (corresponding to WO01/67170 published on Sep. 13, 2001), U.S. Ser. No. 09/759,212, filed on Jan. 11, 2001, U.S. Ser. No. 09/606,654, filed on Jun. 28, 2000 and U.S. Ser. No. 09/784,972, filed on Feb. 15, 2001, all of which are incorporated herein by reference. The improved EPD comprises isolated cells formed from microcups of well-defined shape, size and aspect ratio and filled with charged particles dispersed in a dielectric solvent, preferably a halogenated solvent, particularly a perfluorinated solvent. The filled cells are individually sealed with a polymeric sealing layer, preferably formed from a composition comprising a material selected from a group consisting of thermoplastics, thermosets and their precursors.
All of the previously known and the microcup-based electrophoretic displays may be constructed into the form of a board to be used as e-signs or e-bulletins. A co-pending pending patent application filed by the Applicants of this invention discloses whiteboards implemented with magnetophoretic and electromagnetophoretic display technologies. In this invention, microcup based electrophoretic display is used for whiteboard application. ITO electrode layer is eliminated in the disclosed designs, which further reduces the cost.
The display of the present invention comprises two layers of insulating substrate, at least one of which, usually the one on the viewing side, is transparent, and an array of display cells sandwiched between the two layers of substrate. The display may optionally comprise a conductive layer placed between the cell and one of the substrate layers.
The display cells are filled with an electrophoretic fluid in which charged particles are dispersed in a solvent or solvent mixture. The solvent or solvent mixture may comprise a contrast colorant, which may be a dye or pigment.
The device further comprises a writing means, such as a high voltage electric writing head or a high voltage pen, for generating an image. The writing means may be on the viewing side or behind the non-viewing side.
The device may also optionally comprise an erasing means to electrically erase the image. The erasing means may also be placed on the viewing side or behind the non-viewing side.
Similar to conventional electrophoretic displays (EPDs or EPIDs), whiteboards of this invention are bistable and have a very wide viewing angle. Many different driving mechanisms and circuitry designs may be employed to achieve optimum performances of the displays of this invention. Most of them do not require the use of a transparent conductor film, such as ITO film, which is expensive, fragile and often transmits or reflects less than 90% of the incipient visible light. As a result, the displays of the invention are much more flexible and durable than conventional displays and provide images of high contrast ratio, wide viewing angle and high reflectance in the Dmin area. Furthermore, the present invention provides a great number of alternatives in design, and a particular type of design within the scope of the invention may be easily constructed to meet the needs for a variety of applications.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various drawing figures.